did you read the manifesto? I'm just putting 2 & 2 together. This dude definitely has an agenda, if you can't see that you are blind.

What was the main point of his manifesto?

Clear his name or gun control?
He's a left-leaning lunatic, but his agenda is so firmly in the former (rebel against LAPD, which has nothing to do with gun control) that any agenda concerning the latter takes a back seat.